/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.support;

import java.beans.PropertyEditor;
import java.lang.reflect.Method;

import org.springframework.beans.PropertyEditorRegistry;
import org.springframework.beans.SimpleTypeConverter;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.TypeMismatchException;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MethodInvoker;
import org.springframework.util.ReflectionUtils;

/**
 * Subclass of {@link MethodInvoker} that tries to convert the given
 * arguments for the actual target method via a {@link TypeConverter}.
 *
 * <p>Supports flexible argument conversions, in particular for
 * invoking a specific overloaded method.
 *
 * @author Juergen Hoeller
 * @see org.springframework.beans.BeanWrapperImpl#convertIfNecessary
 * @since 1.1
 */
public class ArgumentConvertingMethodInvoker extends MethodInvoker {

    @Nullable
    private TypeConverter typeConverter;

    private boolean useDefaultConverter = true;

    /**
     * Return the TypeConverter used for argument type conversion.
     * <p>Can be cast to {@link org.springframework.beans.PropertyEditorRegistry}
     * if direct access to the underlying PropertyEditors is desired
     * (provided that the present TypeConverter actually implements the
     * PropertyEditorRegistry interface).
     */
    @Nullable
    public TypeConverter getTypeConverter() {
        if (this.typeConverter == null && this.useDefaultConverter) {
            this.typeConverter = getDefaultTypeConverter();
        }
        return this.typeConverter;
    }

    /**
     * Set a TypeConverter to use for argument type conversion.
     * <p>Default is a {@link org.springframework.beans.SimpleTypeConverter}.
     * Can be overridden with any TypeConverter implementation, typically
     * a pre-configured SimpleTypeConverter or a BeanWrapperImpl instance.
     *
     * @see org.springframework.beans.SimpleTypeConverter
     * @see org.springframework.beans.BeanWrapperImpl
     */
    public void setTypeConverter(@Nullable TypeConverter typeConverter) {
        this.typeConverter = typeConverter;
        this.useDefaultConverter = (typeConverter == null);
    }

    /**
     * Obtain the default TypeConverter for this method invoker.
     * <p>Called if no explicit TypeConverter has been specified.
     * The default implementation builds a
     * {@link org.springframework.beans.SimpleTypeConverter}.
     * Can be overridden in subclasses.
     */
    protected TypeConverter getDefaultTypeConverter() {
        return new SimpleTypeConverter();
    }

    /**
     * Register the given custom property editor for all properties of the given type.
     * <p>Typically used in conjunction with the default
     * {@link org.springframework.beans.SimpleTypeConverter}; will work with any
     * TypeConverter that implements the PropertyEditorRegistry interface as well.
     *
     * @param requiredType type of the property
     * @param propertyEditor editor to register
     * @see #setTypeConverter
     * @see org.springframework.beans.PropertyEditorRegistry#registerCustomEditor
     */
    public void registerCustomEditor(Class<?> requiredType, PropertyEditor propertyEditor) {
        TypeConverter converter = getTypeConverter();
        if (!(converter instanceof PropertyEditorRegistry)) {
            throw new IllegalStateException(
                    "TypeConverter does not implement PropertyEditorRegistry interface: " + converter);
        }
        ((PropertyEditorRegistry) converter).registerCustomEditor(requiredType, propertyEditor);
    }


    /**
     * This implementation looks for a method with matching parameter types.
     *
     * @see #doFindMatchingMethod
     */
    @Override
    protected Method findMatchingMethod() {
        Method matchingMethod = super.findMatchingMethod();
        // Second pass: look for method where arguments can be converted to parameter types.
        if (matchingMethod == null) {
            // Interpret argument array as individual method arguments.
            matchingMethod = doFindMatchingMethod(getArguments());
        }
        if (matchingMethod == null) {
            // Interpret argument array as single method argument of array type.
            matchingMethod = doFindMatchingMethod(new Object[] {getArguments()});
        }
        return matchingMethod;
    }

    /**
     * Actually find a method with matching parameter type, i.e. where each
     * argument value is assignable to the corresponding parameter type.
     *
     * @param arguments the argument values to match against method parameters
     * @return a matching method, or {@code null} if none
     */
    @Nullable
    protected Method doFindMatchingMethod(Object[] arguments) {
        TypeConverter converter = getTypeConverter();
        if (converter != null) {
            String targetMethod = getTargetMethod();
            Method matchingMethod = null;
            int argCount = arguments.length;
            Class<?> targetClass = getTargetClass();
            Assert.state(targetClass != null, "No target class set");
            Method[] candidates = ReflectionUtils.getAllDeclaredMethods(targetClass);
            int minTypeDiffWeight = Integer.MAX_VALUE;
            Object[] argumentsToUse = null;
            for (Method candidate : candidates) {
                if (candidate.getName().equals(targetMethod)) {
                    // Check if the inspected method has the correct number of parameters.
                    Class<?>[] paramTypes = candidate.getParameterTypes();
                    if (paramTypes.length == argCount) {
                        Object[] convertedArguments = new Object[argCount];
                        boolean match = true;
                        for (int j = 0; j < argCount && match; j++) {
                            // Verify that the supplied argument is assignable to the method parameter.
                            try {
                                convertedArguments[j] = converter.convertIfNecessary(arguments[j], paramTypes[j]);
                            } catch (TypeMismatchException ex) {
                                // Ignore -> simply doesn't match.
                                match = false;
                            }
                        }
                        if (match) {
                            int typeDiffWeight = getTypeDifferenceWeight(paramTypes, convertedArguments);
                            if (typeDiffWeight < minTypeDiffWeight) {
                                minTypeDiffWeight = typeDiffWeight;
                                matchingMethod = candidate;
                                argumentsToUse = convertedArguments;
                            }
                        }
                    }
                }
            }
            if (matchingMethod != null) {
                setArguments(argumentsToUse);
                return matchingMethod;
            }
        }
        return null;
    }

}
